This document discusses various types of chemical reactions including: 1) Combination reactions where elements combine to form compounds according to general formulas such as A + B → AB. Examples given are metals reacting with non-metals to form salts, and metals reacting with oxygen to form metal oxides. 2) Decomposition reactions where a single substance breaks down into simpler substances, usually requiring heat. An example given is AB → A + B. 3) Specific decomposition reactions of metal oxides, nitrates, carbonates, and hydrates when heated that produce other substances like oxygen, carbon dioxide, or anhydrous salts.

1. Chemistry III

2.  It is a reaction takes place when two or more
elements combine to form more complex
substance.
 Gen. Formula
 A + B  AB

3. Metal + non metals  Salt
 Mg 2 + Cl1  MgCl2
 Cu + O2  CuO
Metal + Oxygen  Metal Oxide
 Fe4 + O2  Fe2O4
 Mg + O  MgO

4. Metal oxide +Water  Metal Hydroxide
Fe2O4 + H2O  Fe(OH)4
Cu2O + H2O  CuOH
Non-metal + Oxygen  Non-metal oxide
C + O2 CO2
N3 + O2 N2O3

5. Non-metal oxide + Water  Oxyacid
CO2 + H2O  H2CO3
SO2 + H2O  H2SO3
Metal Oxide + Non-metal Oxide  salt
MgO + CO2 MgCO3
MgO + SO3  MgSO4

6. In decomposition reaction , one substance
, usually undergoes a reaction to form two or
more substances which may be elements or
compound.
This process usually requires heat to
complete the reaction
AB  A + B

7. A. When an oxide is heated, generally oxygen is
given off as one of the products.
1. HgO Hg + O2
2. KClO3 KCl + O2

8.  When nitrates are heated, it produces nitrites
and oxygen.
 KNO3 KN O2 + O2

9.  Some carbonates like limestone when
heated, decompose to yield CO2.
 CaCO3 CaO + CO2
 MgCO3 MgO + CO2

10.  Some compounds such as baking soda (
sodium hydrogen carbonate or sodium
bicarbonate ) when decompose will yield
carbon dioxide, water and carbonate salt
 2NaHCO3 Na2CO3+H2O +CO2
 2KHCO3 K2CO3 +H2O +CO2

11.  Hydrates are substances that contain on e or
more molecules of water for each formula
units.These compounds, upon application of
heat, readily decompose.The water is driven
off leaving the anhydrous(without water) salt.
 Na2CO3 + H2O Na2CO3 +H2O